| Crowding is a common malocclusion, the incidence in our country was 60%-70%. Numerous causes crowding, Studies have shown that modern people bone hypoplasia, arch stenosis is an important reason for the formation of crowding. The main clinical methods to solve crowding are arch expansion and extraction treatment. For crowding, stability and aesthetics are the two main factors affecting the choice of treatment. In recent years, studies have shown that arch expansion and extraction treatment have no significant difference in the stability of treatment. Extraction can cause lip retraction, especially for some patients with not plump face type, tooth extraction may affect surface appearance. Contemporary orthodontic theory indicates that unless serious congestion in general can be resolved through non-extraction treatment. Exploit the growth potential of the young patients expanding arch to provide clearance for the crowded dentition is another effective solution for crowding. RPE technology, as a clinical application, has a long history of. In 1860, Mr. Angle, orthodontic profession founder, indicated that by opening palate raphe maxillary arch can be extended. After nearly a century of exploration and practice, 1961 Haas RPE’s invention makes it possible to truly maxillary expansion, From then on, scholars have proposed a variety of maxillary expansion instrument. Currently, rapid palatal expansion technique(RME) in clinical orthodontics has been widely used. However, due to the reason of anatomy, the feasibility of mandibular arch expansion has been questioned. In 1962 Walter summarizing clinical data indicate orthodontic process has increased the mandibular arch width,it is possible to expanse mandbular arch. Sandstrom in 1982 published the first clinical reports on the mandibular arch expansion. After 30 years scholars have reported the clinical trial results and related research of using different devices mandibular arch expansion. During this period, many scholars were studing on the stability of the mandibular arch expansion, and have achieved encouraging results.Mandibular arch extensions can open up the gap, lifting crowded, leveling Spee’s curve, while matching the upper and lower arch width. Treatment principles to surface type is oriented us to pay more attention to the impact of the treatment on soft tissue surface, so we have been actively exploring the non-extraction treatment methods, especially the mandibular arch technology. The past two decades, drawing on the mandibular arch expansion activities of the advantages and disadvantages of Bihelix, Schwarz, Crozat, etc., Professor of Orthodontics in our hospital carried out improvement of mandibular arch expansion, designed and produced a spiral expander jaw fixed steel structure. Hyrax screw expand the maxillary and mandibular improved spiral expand simultaneously applied to the treatment of patients crowding achieved satisfactory treatment outcome. However, any treatment will have an impact on the hard and soft tissue of the patient to achieve a therapeutic effect. Models measuring and X-ray measurements of clinical efficacy evaluation methods commonly used. Dental model can accurately reflect the size of the patient’s teeth, arch form, content-based bone morphology. X-ray film can reflect the relationship between the upper and lower jaw and teeth of patients, record changes in the soft tissue of patients before and after treatment. Measurement model and the using of X-ray measurements, we can make a valid assessment of the clinical results of using maxillomandibular arch expansion technique to correct crowding.Research PurposesIn clinic, young patients’ bone hypoplasia is the main cause of crowding, RPE technology is a commonly used method to increase bone mass and solve the crowding. However, due to the anatomy reasons, the clinical applications and relevant reports about mandibular arch expansion are less. In this study, we selected 12 patients treated with maxillomandibular arch expansion as research object. Patients were models measuring and measuring X-ray photography, to compare measurements before and after treatment. To discuss on how the malliomandibular arch expansion joint fixed appliance influent of patient dental arch form, jaw, and soft tissue surface type, Through the analysis of the results summarized on the scope of the maxilomandibular arch expansion joint treatment, to provide a reference for further clinical application.Research MethodsMen’s and women’s growth and development curves of bone and soft tissue were significantly different, to avoid the impact of gender differences in the efficacy evaluation, the experiment selected 12 female patients from Air Force General Hospital Orthodontics patients ending treatment in 04-11 years. Class Ⅰ skeletal pattern, 0.7o <ANB <4.7o, occlusal relationship is neutral or slightly remote; and after treatment showed no skeletal dysplasia, no obvious front arch sudden, SNA average of 78.83 ± 2.91o, SNB average of 75.29 ° ± 2.46o; maxillary arch crowding amount average 6.08 ± 3.77 mm, the mandibular arch crowding amount average 3.70 ± 2.16mm; treatment method is maxillomandibular arch expansion combined with MBT fixed appliance; and at the end of treatment Patients with dental neat and good occlusion. The tooth models and skull radiographs were taken before treatment and at the end of fixed orthodontic. Model for measuring content before and after treatment and after the end of the model year of treatment on mandibular model cusp 3-3 pitch, and the distance between the central fossa 4-4,5-5,6-6, mainly reflecting the patients before and after treatment arch width arch width to maintain the status change and after treatment. X-ray measurements included SNA, SNB, ANB, MP / SN, U1 / SN, L1 / MP, U1 / NA, U1 / NB, and other indicators, which reflect hard tissue changes, and Holdaway, Burstone and Ricketts’ measurements which reflected the lip and soft tissue changes. All models were measured by the same surveyors and measured twice within a week, taking the average of the two measurements for the final result. All X-ray film measured by the same investigator completed within two months. A same radiograph was measured twice in a month, if there are significant differences in the two measurements for X-ray re-measurement. The average of the two measurements is the measurement result. Data were measured by SPSS13.0 statistical software in Wilcoxon test, to analyze before and after treatment arch changes and maxillofacial and soft tissue changes.Results1. At the end of treatment, mandibular arch width were significantly increased,by using maxillomandibular arch expansion combined with fixed appliance. Maxillary first premolar width increased 7.6mm, the width of the mandibular second premolar increase 7mm, the mandibular arch width between the first molars were increased by about 5mm. Arch width showing an overall increase, in the amount shows that premolar region> molar area> canine area. The arch width changes of premolar and molar region make a significant arch form change occurred, while the front of the arch from the initial narrow round tip type turned into the end of a width wide oval type.2. Three patients’ three years later postrention tooth models were measured, the results show only a small amount of maxillary canine section width recurrence, and molars and premolars width can basically be maintained, and the width between the individual teeth with a small amount increases. After the end of therapy arch width and arch form can basically stable.3. After maxillomandibular arch expansion combined with fixed appliance, index reflects changes in the mandible were not statistically significant, there was not apparent mandibular sagittal position growth or change after treatment. The indicators reflecting changes in in the teeth, especially, incisors associated with the lower axis index L1 / MP, L1 / NA, L1-NB has a statistically significant change. L1 / MP increases 3.33o, L1 / NB average increase of 4.5o, L1-NB average distance increases 1.48 mm, the treatment process took place under the incisor lip inclination. Although the cut after treatment with teeth axis three indicators related to each index were increased but remained within the normal range occur. For U1 / SN analysis shows that the degree of crowding on more than 6mm of patients after treatment will produce incisor lip inclination, while the patient is less than 6mm crowded upper incisors, after RPE a certain degree of income will be generated.4. Soft tissue changes after the treatment. The average distance from the upper lip to line E decrease about 1.15 mm, there is statistically significant change, the lower lip moved forward to the line E about 0.52 mm, but not statistically significant. The lower lip moved forward to the H-line and had statistically significant about 1mm. Distance between the lower lip pits to H line is reduced 0.8mm, and the statistical significance significant. Relative to the Sn-Pg ’upper lip closing 0.42 mm, lower lip forward 0.5mm. But two indicators were no statistically significant changes. Comparison of the normal range of variation with the indicators show that the patient’s soft tissue surface type generally improved. But because of the upper lip retraction and lower lip forward, three patients at the end of the position relative of the upper and lower lips is not beautiful enough.Conclusion1. The maxillomandibular arch expansion shows a significant increase in upper and lower arch width. After the expansion, mandibular arch width occurred significantly increased and the amount of increase in mandible and maxillary are similar, so that it can match the expansion of the maxillary arch. The premolar width impact on arch perimeter greatly, its increase is most notable which provides enough clearance for the crowded dentition. Mandibular expansion joint RPE technology can promote bone remodeling, change arch form, increasing the arch perimeter, effectively solve crowding patients.2. After the maxillomandibular expansion, arch width can effectively maintain treatment, treatment results are stable and long-term reliable.3. Maxillomandibular expansion combined with fixed appliance have no effect on mandibular sagittal and vertical growth. In the treatment, maxillary axis change affected by the crowding level, the smaller the crowding, the more likely adduction front teeth, the greater the degree of crowding, the greater the likelihood of anterior lip dipping. The expansion is difficult to produce improvement on the lower incisor teeth axis. After expansion, patients with a slight lip change, table realized as retraction in the upper lip and lower lip slightly forward. After maxilloandibular expansion, most patients’ soft tissue surfaces type improved, especially the upper lip, is in the E line, which is the soft tissue surface type close to people’s aesthetic standards now. Relative to the upper lip, lower lip has produced a significant advance.4. Because of the age reason treatment, in the clinic, more boys in the growth peak, more appropriate to choice arch expansion. And based on the difference between the soft tissue growth curve, after puberty, male’s nose and chin have greater growth potential. As the growth and development of male patients, their conditions to choose maxillomandibular expansion treatment may be relaxed, while to female patients the indications for treatment should be more rigorous.5. Stability and aesthetic considerations, for the crowded patient, the clinical application of the mandibular arch expansion technology content should be considered are:①Patients with narrow arch form or sharp form should consider applying the treatment.②To crowding patients, those who’s mandibular incisors upright and the posterior segment teeth axis tilt should be selected for treatment on upper and lower arch expansion;③the maxillomandibular expansion treatment is more suitable for these crowding patients whose surface type is straighter, lip protrusion is smaller. And patients with Partial Class Ⅱ surface more suitable to choice expansion appliance.④ treatment of patients younger should consider applying the arch expansion treatment.⑤ compared with female patients, arch expansion appliance should give more consideration to male crowding patients in growth and development. on the contrary,①lower incisor inclination, posterior axis more upright patients crowded mandibular arch expansion has increased incisor dumping, reducing the risk of treatment stability.②while the front lower lip protrusion mandibular arch expansion is difficult to improve the lower lip protrusion, it should be carefully chosen arch expansion appliance. |
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